Although cells are typically present in the body in the form of three-dimensional clusters, in the case of classical plate culturing, cells are cultured in a single layer in a form in which they adhere to a container.
There have been many cases reported in which the properties of cells vary considerably due to differences in the culturing environment. In addition, with respect to suspension culturing in which cells are suspended in a liquid culture medium, although there are cells that are suitable for suspension culturing, there are also cells that are not.
Various types of systems and kits that use these cells have been developed in recent years due to accelerated drug development research and improved evaluation technologies. As exemplified by ELISA kits, which use a color reaction to determine the produced amount of a substance by combining an antigen-antibody reaction and enzyme reaction, and FRET or BRET, which utilize a phenomenon by which energy transfer occurs according to the proximity of two target sites in a form in which it is measured as light, novel methodologies demonstrating high sensitivity, high intensity and high selectivity have been developed through the utilization of numerous principles (NPT 1 and 2).
Among these screening methods, various types of kits and methods have been proposed and implemented based on the principle of cell migration phenomena. Examples of methods that have been developed include a method consisting of fabricating an opening in confluent cultured cells and comparing the phenomenon by which the opening is filled in terms of wound healing rate as described in PTL 1, and a method consisting of punching numerous holes of a fixed size in an insert culture-like structure and comparing the chemotaxis of a compound by cell migration as described in PTL 2. The method described in PTL 2 in particular has already been applied and implemented in various forms. In addition, attempts have also been made in the manner of PTL 3, in which evaluations are carried out by using cell motility per se as the target and monitoring changes in protoplasmic streaming by carefully examining the Brownian movement and protoplasmic streaming of cells, and in the manner of PTL 4, which utilizes inkjet technology to regularly disseminate a large number of cells in narrow regions followed by monitoring and examining the movement thereof.
In the case of using cell motility or migration phenomena for evaluation of new drug development and the like, although this is extremely appealing since it becomes possible to identify interesting properties of cells with respect to quantitative performance and clarity as indicated by prior research, on the other hand, there also many cases requiring extremely complicated systems and intricate apparatuses or cases requiring considerable effort in terms of time and processing, thereby resulting in the desire for the development of easier and faster evaluation methods.
In addition, there are cases in which the status of cells contained in biological samples change corresponding to the status of a portion of or the entire body. For example, treatment methods are known that remove leukocytes that have been activated in associated with some form of disease based on a change in cell status.